This invention relates to a safety system for preventing a user from falling from an elevated structure, and, more particularly, to a safety harness system for use with intermodal cargo containers.
Stackable cargo shipping containers are now one of the most common ways to transport goods around the world via ship, semi-trailer truck or train. These large containers are of standard construction and dimensions for carrying all manner of goods. During use of these containers, it is sometimes necessary for a worker to climb onto the top of a container or a column of stacked containers to perform repair, maintenance or cleaning tasks. For example, when stacked, containers are subject to tearing, denting or puncture damage of the roof of the lower containers which requires prompt repair. Before containers can be moved by trucks on roadways in winter, the roof of each containers must be cleared of any accumulated packed snow to prevent the snow from breaking off during travel and posing a threat to other traffic.
There is always the risk of a fall from the top of the container due to slipping, carelessness or pre-occupation while working at the edges or corners of the containers. Existing containers do not incorporate any tie off or mounting system for worker safety. To address the problem of worker safety on the containers, prior art systems have been developed. At some sites, repair work on containers is conducted in a special shop which includes a raised independent framework below which containers are positioned. The framework provides attachment points for a safety harness to be worn by a worker. The expense and work of transporting containers to the shop makes this approach practical only for damaged containers. Most repair work is performed in the field in remote areas with no overhead structure or crane to lift tools or safety devices into position. Any fall restraint system is therefore, preferably light, portable, easily deployed and flexible so that the worker can carry the system in a tool box or backpack or drape the system over the shoulder allowing hands-free climbing into position on top of the container. In this regard, many prior art devices are cumbersome, heavy and impractical.
U.S. Pat. No. 5,092,426 to Rhodes and U.S. Pat. No. 4,928,790 to Franks disclose safety devices mountable directly to the roof of a container. The systems are bulky and heavy, and require considerable manpower and time to install in place which makes them inefficient and expensive to use.
U.S. Pat. No. 5,036,949 to Crocker et al. discloses an apparatus that requires the worker to go to the edge of the elevated work surface and clamp down the edge hooks with thumb screws. This not only exposes the worker to falling over the edge while deploying the safety apparatus, but is slow and inefficient to deploy. The edge hook is not easily adaptable for attachment to the different edge configurations of containers used in the industry.
Mallard in U.S. Pat. No. 5,004,071 discloses a adapter bracket that is mountable to the corner of a cargo container with a retractable line attachable to a worker. This system also exposes the worker to the possibility of falling over the edge while deploying the system. Locating the bracket in a corner does not offer significant fall restraint protection in the mounting corner.
Flora et al. in U.S. Pat. No. 5,711,397 discloses a safety device that employs a rigid framework extending across the elevated surface. Like Rhodes and Franks, Flora et al. relies on the rigidity of the framework to absorb loads exerted by the restraining line.
In the interests of worker safety and efficiency, and to address the concerns of occupational safety experts, applicant has developed a novel safety system that addresses the drawbacks of the prior art. The system of the present invention provides a lightweight, readily mountable safety system that prevents a worker from approaching too close to the edge of a container or arrests a fall in the event that a worker does slip over the edge. The system of the present invention is designed to be installed by the worker without assistance from others to provide an efficient and reliable safety system.
Accordingly, the present invention provides a system for securing a worker to an elevated structure comprising:
a flexible anchor line extendable across the structure;
hooks at opposite ends of the flexible anchor line for engaging the structure;
a line storage device for releasably storing a portion of the flexible anchor line to adjust the length of line and tension the line to bring the hooks into anchoring engagement with the structure and secure the anchor line to the structure;
a restraining line releasably connectable to the flexible anchor line; and
a harness wearable by the worker connected to the restraining line.
In a preferred arrangement, the hooks of the present invention are adapted to incorporate multiple hook arms to engage and secure the system to various cargo containers designs which incorporate different edge constructions. The hook arms preferably include lips that engage under the container edge to prevent the hook from dislodging in a vertical direction.
The system of the present invention acts to restrain a worker from moving too close to the edge surface of an elevated structure, or, if the restraining line is positioned inadvertently close to the end of the elevated structure, the system acts to arrest a fall when a worker topples over the edge. In addition, once a worker has deployed the system of the present invention from the top of a ladder centred at the ends of a container or from a service platform, the device will arrest a fall by a worker making the final move to the top of the container.